<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>bootstrap入门</title>
    <link rel="stylesheet" href="./bootstrap-5.2.3-dist/css/bootstrap.min.css">
    <style>
        .mybg{
            background-color: aquamarine;
        }  
        .by-border{
            border: 1px solid red;
        } 
        @media screen and (min-width:1200px) and (max-width:1399px) {
            .col-xl-2{
            width: 20%;
        } 
        }    
        
    </style>
</head>
<body>    
    <div class="container">
        <div class="row">
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">1</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">2</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">3</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">4</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">5</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">6</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">7</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">8</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">9</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">10</div>
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">11</div>            
            <div class="col-12 col-sm-6 col-md-4 col-lg-3 col-xl-2 col-xxl-2  by-border">12</div>
        </div> 
    </div>   
    <div class="container">
        <div class="row">
            <div class="by-border col-3">1</div>
            <div class="by-border col-3 offset-md-1">2</div>
            <div class="by-border col-3">3</div>
        </div>

    </div> 
    <script src="./bootstrap-5.2.3-dist/js/bootstrap.min.js"></script>    
</body>
</html>